Preheat your oven to 250° Fahrenheit and pull the tri-tip from the refrigerator. Pat dry and allow to come to room temperature.
Combine the spices, salt and pepper in a small bowl and massage into the tri-tip. Transfer the roast to a sheet pan with a wire rack and place on the centre rack of your oven. Cook until the roast reaches an internal temp of 120’ for rare, 125° for medium rare and 130° for medium, approximately 45 minutes to an hour. When the desired temperature is reached, remove from the oven and loosely cover with foil. Allow to rest for 10 minutes.
After the roast has rested, in a heavy cast iron skillet, melt the butter and oil over medium high heat and quickly sear the roast on all sides, basting with the butter and oil from the pan.